1. Field of the Invention
This invention relates to an improved method of recovering high purity N-acyl taurines in high yield.
2. Description of the Prior Art
The Schotten-Baumann reaction is a well-known and highly useful means for acylating taurine compounds by reaction therewith of a carboxylic acid chloride in the presence of alkali. This reaction may be illustrated by the following equation: EQU RCOCl+HNR.sup.1 --CHR.sup.2 --CHR.sup.2 --SO.sub.3 M--+MOH.fwdarw.RCONR.sup.1 --CHR.sup.2 --CH--R.sup.2 --SO.sub.3 M+MCl+H.sub.2 O
wherein:
R is a C.sub.5-19 hydrocarbon radical, PA1 R.sup.1 is H or a C.sub.1-6 hydrocarbon radical, PA1 R.sup.2 is independently H, methyl or ethyl, and PA1 M is alkali metal, e.g. Li, K, or preferably Na.
It is apparent that in the above reaction for the production of Igepon T type (GAF Corporation) anionic surfactants, a considerable quantity of salt is produced as a by-product. The presence of common salt as a contaminant in anionic surface active agents of the "Igepon" type has been recognized not only by the patentees of U.S. Pat. No. 1,932,180, particularly Example 37 and the description thereafter, but also by the teachings of German Pat. No. 664,309, in which an attempt was made to prepare an anionic surface active agent substantially free from salt by reacting the fatty acid amide with a chloroethane sulfonic acid salt in an inert medium capable of dissolving the desired "Igepon", filtering the "Igepon" free from salt and recovering the substantially salt-free "Igepon" by evaporation of the filtrate. Inasmuch as contamination by inorganic salts in commercial "Igepons" is of ever increasing importance due to their corrosive effect in the packaging of heavy duty liquid detergents, adverse hygroscopic and/or taste effect in synthetic soap bars, toothpastes and mold lubricants, and undesirability in certain emulsion polymerization reactions, renewed activity and efforts have been made to devise processes which would yield substantially salt-free products.
A number of patents describe processes for preparation and recovery of such salt-free N-acyl taurines, including U.S. Pat. Nos. 2,987,526; 2,844,610; 2,844,611; and 4,233,229. All of these techniques, however, suffer from the disadvantage that they do not enable the recovery of a high purity product in high yield.
Accordingly, it is the object of this invention to provide an improved method of recovering N-acyl taurines in high yield, relatively and/or substantially free of salt.